Custom-engineered chimeric foot-and-mouth disease vaccine elicits protective immune responses in pigs

Chimeric foot-and-mouth disease viruses (FMDV) of which the antigenic properties can be readily manipulated is a potentially powerful approach in the control of foot-and-mouth disease (FMD) in sub-Saharan Africa. FMD vaccine application is complicated by the extensive variability of the South African Territories (SAT) type viruses, which exist as distinct genetic and antigenic variants in different geographical regions. A cross-serotype chimeric virus, vKNP/SAT2, was engineered by replacing the external capsid-encoding region (1B-1D/2A) of an infectious cDNA clone of the SAT2 vaccine strain, ZIM/7/83, with that of SAT1 virus KNP/196/91. The vKNP/SAT2 virus exhibited comparable infection kinetics, virion stability and antigenic profiles to the KNP/196/91 parental virus, thus indicating that the functions provided by the capsid can be readily exchanged between serotypes. As these qualities are necessary for vaccine manufacturing, high titres of stable chimeric virus were obtained. Chemically inactivated vaccines, formulated as double-oil-in-water emulsions, were produced from intact 146S virion particles of both the chimeric and parental viruses. Inoculation of guinea pigs with the respective vaccines induced similar antibody responses. In order to show compliance with commercial vaccine requirements, the vaccines were evaluated in a full potency test. Pigs vaccinated with the chimeric vaccine produced neutralizing antibodies and showed protection against homologous FMDV challenge, albeit not to the same extent as for the vaccine prepared from the parental virus. These results provide support that chimeric vaccines containing the external capsid of field isolates can be successfully produced and that they induce protective immune responses in FMD host species.This work was supported by funding from Intervet SPAH.http://vir.sgmjournals.org/nf201

Spatial distribution of foot-and-mouth disease (FMD) outbreaks in South Africa (2005–2016)

Foot-and-mouth disease (FMD) is a transboundary animal disease that has negative socioeconomic consequences including impacts on food security. In South Africa, FMD outbreaks in communal farming communities cause major livestock and human livelihood concerns; they raise apprehensions about the effectiveness of FMD control measures within the FMD protection areas. This study aimed to identify high-risk areas for FMD outbreaks at the human/domestic animal/wildlife interface of South Africa. Cuzick-Edwards tests and Kulldorff scan statistics were used to detect spatial autocorrelation and spatial–temporal clusters of FMD outbreaks for the years 2005–2016. Four high-risk clusters were identified and the spatial distribution of outbreaks in cattle were closer to game reserve fences and consistent with wildlife contacts as a main contributor of FMD occurrence. Strategic allocation of resources, focused control measures, and cooperation between the affected provinces are recommended to reduce future outbreaks. Further research is necessary to design cost-effective control strategies for FMD.The South African National Research Foundation (NRF)http://link.springer.com/journal/11250hj2022Production Animal Studie

Efficacy of a foot-and-mouth disease vaccine against a heterologous SAT1 virus challenge in goats

Please read abstract in the article.The National Research Foundation (NRF), South Africa and the Peace Parks Foundation.http://www.elsevier.com/locate/vaccinehj2021Production Animal Studie

A comparison of risk factor investigation and experts’ opinion elicitation analysis for identifying foot-and-mouth disease (FMD) high-risk areas within the FMD protection zone of South Africa (2007–2016)

Foot-and-mouth disease is a controlled disease in accordance with the South African Animal Diseases Act (Act 35 of 1984). The country was classified by the World Organisation for Animal Health (WOAH) as having a FMD free zone without vaccination in 1996. However, this status was suspended in 2019 due to a FMD outbreak outside the controlled zones. FMD control in South Africa includes animal movement restrictions placed on cloven-hoofed species and products, prophylactic vaccination of cattle, clinical surveillance of susceptible species, and disease control fencing to separate livestock from wildlife reservoirs. The objectives of this study were to evaluate differences in identifying high-risk areas for FMD using risk factor and expert opinion elicitation analysis. Differences in risk between FMD introduction and FMD spread within the FMD protection zone with vaccination (PZV) of South Africa (2007–2016) were also investigated. The study was conducted in the communal farming area of the FMD PZV, which is adjacent to wildlife reserves and characterised by individual faming units. Eleven risk factors that were considered important for FMD occurrence and spread were used to build a weighted linear combination (WLC) score based on risk factor data and expert opinion elicitation. A multivariable conditional logistic regression model was also used to calculate predicted probabilities of a FMD outbreak for all dip-tanks within the study area. Smoothed Bayesian kriged maps were generated for 11 individual risk factors, overall WLC scores for FMD occurrence and spread and for predicted probabilities of a FMD outbreak based on the conditional logistic regression model. Descriptively, vaccine matching was believed to have a great influence on both FMD occurrence and spread. Expert opinion suggested that FMD occurrence was influenced predominantly by proximity to game reserves and cattle density. Cattle populations and vaccination practices were considered most important for FMD spread. Highly effective cattle inspections were observed within areas that previously reported FMD outbreaks, indicating the importance of cattle inspection (surveillance) as a necessary element of FMD outbreak detection. The multivariable conditional logistic regression analysis, which was consistent with expert opinion elicitation; identified three factors including cattle population density (OR 3.87, 95% CI 1.47–10.21) and proximities to game reserve fences (OR 0.82, 95% CI 0.73–0.92) and rivers (OR 1.04, 95% CI 1.01–1.07) as significant factors for reported FMD outbreaks. Regaining and maintaining an FMD-free status without vaccination requires frequent monitoring of high-risk areas and designing targeted surveillance.The National Research Foundation of South Africa.https://www.elsevier.com/locate/prevetmedhj2024Production Animal StudiesSDG-03:Good heatlh and well-beingSDG-15:Life on lan

Serological evidence of vaccination and perceptions concerning foot-and-mouth disease control in cattle at the wildlife-livestock interface of the Kruger National Park, South Africa

Communal livestock farming areas adjoining the Greater Kruger National Park Area within South Africa are part of the Foot-and-mouth disease (FMD) Protection Zone with Vaccination due to the proximity to wildlife reservoirs. FMD and its control affect the productivity of resource-poor farmers who often depend on livestock for their livelihoods. A cross-sectional study was performed with the objectives to evaluate the perceptions of farmers concerning FMD control, estimate the proportion of cattle with presumed protective antibody titres against FMD, as well as the proportion of herds with adequate herd immunity at the wildlife-livestock interface within Mpumalanga Province. One hundred and four farmers were interviewed with 73% (76/104) being cattle owners and the remainder hired cattle herders. The majority of respondents (79%, 82/104) reported a high level of satisfaction with the current animal health programmes in general. The educational level of the respondents varied by satisfaction level: the median (interquartile range; IQR) education level was standard 9 (2–12) for non-satisfied respondents, standard 3 (0–6) for little satisfied and standard 7 (2–11) for very satisfied respondents (P = 0.036). Animals are not always treated at FMD inspections points, but satisfied respondents were more likely to seek veterinary assistance (P = 0.001). The majority of respondents (92%, 96/104) identified the African buffalo (Syncerus caffer) as a risk factor for FMD outbreaks. Liquid-phase blocking ELISA antibody titres ≥1.6log10 were used to indicate positive serology secondary to FMD vaccination. At the time of sampling and relative to this threshold, 23% (95% confidence interval (CI): 12%–34%) of the sampled cattle had positive serology to SAT-1, 41% (95%CI: 33%–48%) to SAT-2 and 29% (95%CI: 19%–39%) to SAT-3. The median (IQR) time between the previous vaccination and sampling was 189 (168–241) days. The sampled cattle had a longer inter-vaccination interval as scheduled by state veterinary services and antibody levels were low at the time of the study. The majority of respondents expressed high satisfaction with the currently applied FMD vaccination programme, which provides an opportunity for progressive adaption of animal health programmes within the study area.This work was funded by contract agreement with the Peace Parks Foundation (Project No. A0U199), with additional support from the Research Development Programme (Project No. A0T384) at the University of Pretoria and Incentive Funding for Rated Researchers from the National Research Foundation (Project No. 76734).http://www.elsevier.com/locate/prevetmedhj2019Production Animal Studie

Tracking the antigenic evolution of foot-and-mouth disease virus

Quantifying and predicting the antigenic characteristics of a virus is something of a holy grail for infectious disease research because of its central importance to the emergence of new strains, the severity of outbreaks, and vaccine selection. However, these characteristics are defined by a complex interplay of viral and host factors so that phylogenetic measures of viral similarity are often poorly correlated to antigenic relationships. Here, we generate antigenic phylogenies that track the phenotypic evolution of two serotypes of footand- mouth disease virus by combining host serology and viral sequence data to identify sites that are critical to their antigenic evolution. For serotype SAT1, we validate our antigenic phylogeny against monoclonal antibody escape mutants, which match all of the predicted antigenic sites. For serotype O, we validate it against known sites where available, and otherwise directly evaluate the impact on antigenic phenotype of substitutions in predicted sites using reverse genetics and serology. We also highlight a critical and poorly understood problem for vaccine selection by revealing qualitative differences between assays that are often used interchangeably to determine antigenic match between field viruses and vaccine strains. Our approach provides a tool to identify naturally occurring antigenic substitutions, allowing us to track the genetic diversification and associated antigenic evolution of the virus. Despite the hugely important role vaccines have played in enhancing human and animal health, vaccinology remains a conspicuously empirical science. This study advances the field by providing guidance for tuning vaccine strains via site-directed mutagenesis through this high-resolution tracking of antigenic evolution of the virus between rare major shifts in phenotype.S1 Data. VNT serological results for serotype O viruses and antisera.S2 Data. LPBE serological results for serotype O viruses and antisera.S3 Data. VNT serological results for serotype SAT1 viruses and antisera.S1 Table. Foot-and-mouth disease virus details with accession numbers.S2 Table. Pan-serotypic reference alignment of FMDV. The dataset shows the aligned VP2, VP3 and VP1 proteins of example SAT1 and O isolates used in the study alongside representative isolates from the other five serotypes. The four contiguous surface-exposed structural motifs confirmed as containing antigenic sites on at least four serotypes are highlighted in red–locations are approximate due to structural differences between the serotypes. The RGD cell surface receptor-binding motif, in the centre of the third site, is highlighted in blue.S3 Table. Residues identified as part of epitopes on structural proteins across the six tested serotypes of FMDV, along with corresponding positions on all serotypes.S4 Table. SAT1 mar-mutants.The authors acknowledge the Biotechnology and Biological Sciences Research Council (BBSRC) Institute Strategic Programme on Livestock Viral Diseases at The Pirbright Institute (BB/J004375/1) [RR SP DJP MM] and BBSRC BB/ G529532/1 [DWB MM], BB/F009186/1 [MM] and BBSRC BB/L004828 [RR] and BBSRC / Department for International Development / Scottish Government grants BB/H009302/1 [RR] and BB/H009175/1 [SP FFM RR] (http://www.bbsrc.ac.uk), and Department for Environment, Food and Rural Affairs grant SE2937 (http://www.gov.uk/defra) [MM]. The Food and Agriculture Organisation financially supported the research to determine one-way relationship and antigenic relatedness of SAT1 viruses under grants OSRO/RAF/721/EC and MTF/INT/003/EEC (http:// www.fao.org) [FFM AL JJE BB], and RMRSA (http:// www.rmrdsa.co.za) (Improving detection and characterisation methods for FMDV and ASFV for cattle and pigs in the SADC region) [BB]. Structural studies supported by the UK Medical Research Council grant MR/N00065X/1 [EEF] (http://www.mrc. ac.uk). The work of the Wellcome Trust Centre in Oxford is supported by the Wellcome Trust core award 090532/Z/07/Z [EEF] (http://www.wellcome.ac. uk).http://www.plosone.orgam2016Microbiology and Plant PathologyProduction Animal Studie

Sequence-based prediction for vaccine strain selection and identification of antigenic variability in foot-and-mouth disease virus

Identifying when past exposure to an infectious disease will protect against newly emerging strains is central to understanding the spread and the severity of epidemics, but the prediction of viral cross-protection remains an important unsolved problem. For foot-and-mouth disease virus (FMDV) research in particular, improved methods for predicting this cross-protection are critical for predicting the severity of outbreaks within endemic settings where multiple serotypes and subtypes commonly co-circulate, as well as for deciding whether appropriate vaccine(s) exist and how much they could mitigate the effects of any outbreak. To identify antigenic relationships and their predictors, we used linear mixed effects models to account for variation in pairwise cross-neutralization titres using only viral sequences and structural data. We identified those substitutions in surface-exposed structural proteins that are correlates of loss of cross-reactivity. These allowed prediction of both the best vaccine match for any single virus and the breadth of coverage of new vaccine candidates from their capsid sequences as effectively as or better than serology. Sub-sequences chosen by the model-building process all contained sites that are known epitopes on other serotypes. Furthermore, for the SAT1 serotype, for which epitopes have never previously been identified, we provide strong evidence - by controlling for phylogenetic structure - for the presence of three epitopes across a panel of viruses and quantify the relative significance of some individual residues in determining cross-neutralization. Identifying and quantifying the importance of sites that predict viral strain cross-reactivity not just for single viruses but across entire serotypes can help in the design of vaccines with better targeting and broader coverage. These techniques can be generalized to any infectious agents where cross-reactivity assays have been carried out. As the parameterization uses pre-existing datasets, this approach quickly and cheaply increases both our understanding of antigenic relationships and our power to control disease

Improved vaccines for foot-and-mouth disease control : evaluation of a chimera-derived FMD vaccine in relation to a current SAT type vaccine

Foot-and-mouth disease virus (FMDV), a member of the Picornaviridae, causes a highly contagious disease that affects cloven-hoofed animals and leads to production losses, especially in intensive farming systems. In sub-Saharan Africa, control of the disease is complicated by the extensive variability of the South African Territories (SAT) type viruses, which exist as distinct genetic and antigenic variants in different geographical regions. Improved control of FMD, therefore, requires vaccines to be custom-made to specific geographical areas. In this regard, a potentially powerful approach involves the engineering of chimeric FMDV of which the antigenic properties can be readily manipulated. Consequently, the aim of this study was essentially to evaluate a custom-engineered chimeric FMD vaccine in relation to a current SAT type vaccine. To enable the selection of vaccine strains that would provide the best vaccine match against emerging viruses, phylogenetic, genetic and antigenic analyses of SAT serotypes prevalent in sub-Saharan Africa was performed. The results indicated that although SAT1 and SAT2 viruses displayed similar genetic variation within each serotype, antigenic disparity, as measured by r1-values, was less pronounced for SAT1 viruses compared with SAT2 viruses. Consequently, the SAT1 virus KNP/196/91 was selected and a cross-serotype chimeric virus, vKNP/SAT2, was engineered by replacing the external capsid-encoding region (1B-1D/2A) of an infectious cDNA clone of the SAT2 vaccine strain, ZIM/7/83, with that of KNP/196/91. The population diversity of the cell-adapted chimeric virus and pig-adapted KNP/196/91 virus was investigated by means of pyrosequencing; the results of which indicated that the population diversity of the respective viruses was indeed comparable to each other. Subsequently, chemically inactivated vaccines were produced from intact 146S virion particles of both the chimeric and parental viruses and evaluated in a full potency test. Pigs vaccinated with the chimeric vaccine produced neutralising antibodies and showed protection against homologous FMDV challenge. Cumulatively, the data provide support that chimeric vaccines containing the external capsid of field isolates can be successfully produced and that they induce protective immune responses in FMD host species. The potential therefore exists to generate more effective newgeneration chemically inactivated-FMD vaccines that are custom-engineered and specifically produced for geographical areas.Thesis (PhD)--University of Pretoria, 2012.Microbiology and Plant PathologyUnrestricte

Analysis of SAT Type Foot-And-Mouth Disease Virus Capsid Proteins and the Identification of Putative Amino Acid Residues Affecting Virus Stability

<div><p>Foot-and-mouth disease virus (FMDV) initiates infection by adhering to integrin receptors on target cells, followed by cell entry and disassembly of the virion through acidification within endosomes. Mild heating of the virions also leads to irreversible dissociation into pentamers, a characteristic linked to reduced vaccine efficacy. In this study, the structural stability of intra- and inter-serotype chimeric SAT2 and SAT3 virus particles to various conditions including low pH, mild temperatures or high ionic strength, was compared. Our results demonstrated that while both the SAT2 and SAT3 infectious capsids displayed different sensitivities in a series of low pH buffers, their stability profiles were comparable at high temperatures or high ionic strength conditions. Recombinant vSAT2 and intra-serotype chimeric viruses were used to map the amino acid differences in the capsid proteins of viruses with disparate low pH stabilities. Four His residues at the inter-pentamer interface were identified that change protonation states at pH 6.0. Of these, the H145 of VP3 appears to be involved in interactions with A141 in VP3 and K63 in VP2, and may be involved in orientating H142 of VP3 for interaction at the inter-pentamer interfaces.</p></div